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ISDN (Integrated Services Digital Network)

There are two forms of ISDN: PRI and BRI. BRI interface supports a total signaling rate of 144 kbps, which is divided up into two B or bearer channels, which run at 64 kbps, and a D or data channel, which runs at 16 kbps. The bearer channels carry the actual voice, video, or data information, and the D channel is used for signaling. PRI or primary rate interface provides the same throughput as a T1 1. 544 Mbps, has 23 B or bearer channels, which run at 64 kbps, and a D or data channel, which runs at 16 kbps.


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An ISDN service type that provides two B, or data, channels and one D, or management, channel. Each B channel offers 64 Kbps, and the D channel offers 16 Kbps. Supports a total signaling rate of 144 kbps, which is divided into two B or bearer channels running at 64 kbps, and a D or data channel runing at 16 kbps. The bearer channels carry the actual voice, video, or data information, and the D channel is used for signaling.
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A digital end-to-end communications mechanism. ISDN was developed by telephone companies to support high-speed digital communications over the same equipment and infrastructure that is used to carry voice communications. An emerging technology that is beginning to be offered by the telephone carriers of the world. ISDN combines voice and digital network services in a single medium, making it possible to offer customers digital data services as well as voice connections through a single wire. The standards that define ISDN are specified by ITUTSS.
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An independent category of service such as operating system services, communication services and data management services. Each primary service provides a discrete set of functionality. Each primary service inherently includes generic qualities such as usability, manageability and security. Security services are therefore not primary services but are invoked as part of the provision of primary services by the primary service provider.
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<strong>Maturity Level Details:</strong><p style="margin: 0.8em 0px 1em; padding: 0px; text-align: justify; color: rgb(0, 0, 0); font-family: Helvetica, Arial, sans-serif; font-size: 12px;">Maturity levels consist of a predefined set of process areas. The maturity levels are measured by the achievement of the&nbsp;specific&nbsp;and&nbsp;generic goals&nbsp;that apply to each predefined set of process areas. The following sections describe the characteristics of each maturity level in detail.</p><strong>Maturity Level 1 - Initial</strong><br>At maturity level 1, processes are usually ad hoc and chaotic. The organization usually does not provide a stable environment. Success in these organizations depends on the competence and heroics of the people in the organization and not on the use of proven processes.<p style="margin: 0.8em 0px 1em; padding: 0px; text-align: justify; color: rgb(0, 0, 0); font-family: Helvetica, Arial, sans-serif; font-size: 12px;">Maturity level 1 organizations often produce products and services that work; however, they frequently exceed the budget and schedule of their projects.</p><p style="margin: 0.8em 0px 1em; padding: 0px; text-align: justify; color: rgb(0, 0, 0); font-family: Helvetica, Arial, sans-serif; font-size: 12px;">Maturity level 1 organizations are characterized by a tendency to over commit, abandon processes in the time of crisis, and not be able to repeat their past successes.</p><strong>Maturity Level 2 - Managed</strong><br>At maturity level 2, an organization has achieved all the&nbsp;specific&nbsp;and&nbsp;generic goals&nbsp;of the maturity level 2 process areas. In other words, the projects of the organization have ensured that requirements are managed and that processes are planned, performed, measured, and controlled.<p style="margin: 0.8em 0px 1em; padding: 0px; text-align: justify; color: rgb(0, 0, 0); font-family: Helvetica, Arial, sans-serif; font-size: 12px;">The process discipline reflected by maturity level 2 helps to ensure that existing practices are retained during times of stress. When these practices are in place, projects are performed and managed according to their documented plans.</p><p style="margin: 0.8em 0px 1em; padding: 0px; text-align: justify; color: rgb(0, 0, 0); font-family: Helvetica, Arial, sans-serif; font-size: 12px;">At maturity level 2, requirements, processes, work products, and services are managed. The status of the work products and the delivery of services are visible to management at defined points.</p><p style="margin: 0.8em 0px 1em; padding: 0px; text-align: justify; color: rgb(0, 0, 0); font-family: Helvetica, Arial, sans-serif; font-size: 12px;">Commitments are established among relevant stakeholders and are revised as needed. Work products are reviewed with stakeholders and are controlled.</p><p style="margin: 0.8em 0px 1em; padding: 0px; text-align: justify; color: rgb(0, 0, 0); font-family: Helvetica, Arial, sans-serif; font-size: 12px;">The work products and services satisfy their specified requirements, standards, and objectives.</p><strong>Maturity Level 3 - Defined</strong><br>At maturity level 3, an organization has achieved all the&nbsp;specific&nbsp;and&nbsp;generic goals&nbsp;of the process areas assigned to maturity levels 2 and 3.<p style="margin: 0.8em 0px 1em; padding: 0px; text-align: justify; color: rgb(0, 0, 0); font-family: Helvetica, Arial, sans-serif; font-size: 12px;">At maturity level 3, processes are well characterized and understood, and are described in standards, procedures, tools, and methods.</p><p style="margin: 0.8em 0px 1em; padding: 0px; text-align: justify; color: rgb(0, 0, 0); font-family: Helvetica, Arial, sans-serif; font-size: 12px;">A critical distinction between maturity level 2 and maturity level 3 is the scope of standards, process descriptions, and procedures. At maturity level 2, the standards, process descriptions, and procedures may be quite different in each specific instance of the process (for example, on a particular project). At maturity level 3, the standards, process descriptions, and procedures for a project are tailored from the organization's set of standard processes to suit a particular project or organizational unit. The organization's set of standard processes includes the processes addressed at maturity level 2 and maturity level 3. As a result, the processes that are performed across the organization are consistent except for the differences allowed by the tailoring guidelines.</p><p style="margin: 0.8em 0px 1em; padding: 0px; text-align: justify; color: rgb(0, 0, 0); font-family: Helvetica, Arial, sans-serif; font-size: 12px;">Another critical distinction is that at maturity level 3, processes are typically described in more detail and more rigorously than at maturity level 2. At maturity level 3, processes are managed more proactively using an understanding of the interrelationships of the process activities and detailed measures of the process, its work products, and its services.</p><strong>Maturity Level 4 - Quantitatively Managed</strong><br>At maturity level 4, an organization has achieved all the&nbsp;specific goals&nbsp;of the process areas assigned to maturity levels 2, 3, and 4 and the&nbsp;generic goals&nbsp;assigned to maturity levels 2 and 3.<p style="margin: 0.8em 0px 1em; padding: 0px; text-align: justify; color: rgb(0, 0, 0); font-family: Helvetica, Arial, sans-serif; font-size: 12px;">At maturity level 4 Subprocesses are selected that significantly contribute to overall process performance. These selected subprocesses are controlled using statistical and other quantitative techniques.</p><p style="margin: 0.8em 0px 1em; padding: 0px; text-align: justify; color: rgb(0, 0, 0); font-family: Helvetica, Arial, sans-serif; font-size: 12px;">Quantitative objectives for quality and process performance are established and used as criteria in managing processes. Quantitative objectives are based on the needs of the customer, end users, organization, and process implementers. Quality and process performance are understood in statistical terms and are managed throughout the life of the processes.</p><p style="margin: 0.8em 0px 1em; padding: 0px; text-align: justify; color: rgb(0, 0, 0); font-family: Helvetica, Arial, sans-serif; font-size: 12px;">For these processes, detailed measures of process performance are collected and statistically analyzed. Special causes of process variation are identified and, where appropriate, the sources of special causes are corrected to prevent future occurrences.</p><p style="margin: 0.8em 0px 1em; padding: 0px; text-align: justify; color: rgb(0, 0, 0); font-family: Helvetica, Arial, sans-serif; font-size: 12px;">Quality and process performance measures are incorporated into the organization.s measurement repository to support fact-based decision making in the future.</p><p style="margin: 0.8em 0px 1em; padding: 0px; text-align: justify; color: rgb(0, 0, 0); font-family: Helvetica, Arial, sans-serif; font-size: 12px;">A critical distinction between maturity level 3 and maturity level 4 is the predictability of process performance. At maturity level 4, the performance of processes is controlled using statistical and other quantitative techniques, and is quantitatively predictable. At maturity level 3, processes are only qualitatively predictable.</p><strong>Maturity Level 5 - Optimizing</strong><br>At maturity level 5, an organization has achieved all the&nbsp;specific goals&nbsp;of the process areas assigned to maturity levels 2, 3, 4, and 5 and the&nbsp;generic goals&nbsp;assigned to maturity levels 2 and 3.<p style="margin: 0.8em 0px 1em; padding: 0px; text-align: justify; color: rgb(0, 0, 0); font-family: Helvetica, Arial, sans-serif; font-size: 12px;">Processes are continually improved based on a quantitative understanding of the common causes of variation inherent in processes.</p><p style="margin: 0.8em 0px 1em; padding: 0px; text-align: justify; color: rgb(0, 0, 0); font-family: Helvetica, Arial, sans-serif; font-size: 12px;">Maturity level 5 focuses on continually improving process performance through both incremental and innovative technological improvements.</p><p style="margin: 0.8em 0px 1em; padding: 0px; text-align: justify; color: rgb(0, 0, 0); font-family: Helvetica, Arial, sans-serif; font-size: 12px;">Quantitative process-improvement objectives for the organization are established, continually revised to reflect changing business objectives, and used as criteria in managing process improvement.</p><p style="margin: 0.8em 0px 1em; padding: 0px; text-align: justify; color: rgb(0, 0, 0); font-family: Helvetica, Arial, sans-serif; font-size: 12px;">The effects of deployed process improvements are measured and evaluated against the quantitative process-improvement objectives. Both the defined processes and the organization's set of standard processes are targets of measurable improvement activities.</p><p style="margin: 0.8em 0px 1em; padding: 0px; text-align: justify; color: rgb(0, 0, 0); font-family: Helvetica, Arial, sans-serif; font-size: 12px;">Optimizing processes that are agile and innovative depends on the participation of an empowered workforce aligned with the business values and objectives of the organization. The organization's ability to rapidly respond to changes and opportunities is enhanced by finding ways to accelerate and share learning. Improvement of the processes is inherently part of everybody's role, resulting in a cycle of continual improvement.</p><p style="margin: 0.8em 0px 1em; padding: 0px; text-align: justify; color: rgb(0, 0, 0); font-family: Helvetica, Arial, sans-serif; font-size: 12px;">A critical distinction between maturity level 4 and maturity level 5 is the type of process variation addressed. At maturity level 4, processes are concerned with addressing special causes of process variation and providing statistical predictability of the results. Though processes may produce predictable results, the results may be insufficient to achieve the established objectives. At maturity level 5, processes are concerned with addressing common causes of process variation and changing the process (that is, shifting the mean of the process performance) to improve process performance (while maintaining statistical predictability) to achieve the established quantitative process-improvement objectives.</p>
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Highdatarate Digital Subscriber lLne. One of four DSL technologies. HDSL delivers 1. 544 Mbps of bandwidth each way over two copper twisted pairs. Because HDSL provides T1 speed, telephone companies have been using HDSL to provision local access to T1 services whenever possible. The operating range of HDSL is limited to 12,000 feet (3658. 5 meters), so signal repeaters are installed to extend the service. HDSL requires two twisted pairs, so it is deployed primarily for PBX network connections, digital loop carrier systems, interexchange POPs, Internet servers, and private data networks. Compare with ADSL, SDSL, and VDSL.
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